LONDON, March 20 (Thomson Reuters Foundation) - Nearly half of the estimated 56 million abortions carried out worldwide each year are unsafe, leading to the deaths of at least 22,800 women every year, according to a major study published on Tuesday.

Abortion bans do not stop women having terminations, but do increase the risk that they will resort to dangerous measures to end unwanted pregnancies, the Guttmacher Institute said in the most comprehensive report on global abortion trends in a decade.

And although abortion rates have fallen sharply in developed regions in the last 25 years, there has been no notable change in developing countries, it said.

A major factor is the lack of access to good contraception in many regions, resulting in high rates of unplanned pregnancy, the New York-based institute said in a statement.

"Most women who have an abortion do so because they did not intend to become pregnant in the first place," the report's co-author Susheela Singh said in a statement.

"Meeting the need for contraception is critical to bringing down rates even further."

The abortion rate in countries where terminations are largely or totally prohibited is about the same as the rate in countries without restrictions, according to data published by the institute.

It found the highest annual rate of abortion is in the Caribbean - estimated at 59 per 1,000 women of reproductive age; the lowest is in Western Europe at 16 per 1,000 women.

Between 2000 and 2017, 33 countries - including Nepal, Uruguay, Niger and Ethiopia - eased abortion rules, the report said. Nicaragua was the only country to tighten its law.

But the authors warned that some countries with broadly liberal laws had added restrictions eroding access to abortion, including the United States, Russia, Hungary and Latvia.

Two-fifths of women still live in countries where abortion is banned or highly restricted, the report said.

However the increased use of the abortion-inducing drug misoprostol has improved safety, it added.

Projections suggest deaths from unsafe abortions would decline by two-thirds in developing regions if women used misoprostol instead of resorting to riskier procedures.

The authors suggested countries could follow the example of Uruguay which provides information on misoprostol, but not the drug itself, in order to reduce misuse.

The report urged governments to ensure women have access to contraceptive services, to ease abortion laws and to expand access to abortion services and post-abortion care.

It also called for efforts to tackle stigma around abortion which it said leads many women - even in countries where abortion is legal - to seek clandestine terminations and to delay getting treatment for complications. (Reporting by Emma Batha, Editing by Robert Carmichael. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, which covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit news.trust.org to see more stories.)